1. Field of the Invention
The present invention relates to an air conditioner for use in vehicles and, more particularly, to an air conditioner for use in vehicles comprising a compressor operated by an engine and by an electric motor during stopping of the engine.
2. Description of the Related Art
It is a recent trend to manufacture automobiles, which possess an idle stop function so as to meet requirements for improving fuel consumption of an automobile. However, because auxiliary machineries, which are driven by an engine during idle stop mode, are stopped, for example, a compressor of an air conditioner is also stopped. The idle stop in summer has a problem in commercial value from the viewpoint of comfort.
It may be an attempt to take measures of not performing the idle stop during operation of the air conditioner. This idea, however, is far from achieving an essential object of improving fuel consumption.
FIG. 6 shows another attempt in which the following measures are taken. In this attempt, a crank pulley 19 and a crank shaft are brought into disconnection by means of an electromagnetic clutch 20, and a motor generator 3 that starts an engine 1 or generates an electric power is operated as an electric motor by an inverter 21 during idle stop mode. Furthermore auxiliary machineries connected to a belt 2 are driven thereby eventually driving an air-conditioning compressor 11.
Nevertheless, this attempt needs to drive the other auxiliary machineries only for driving the vehicle air-conditioning compressor 11 resulting in a problem of a large unnecessary loss.
Moreover, since the motor generator 3 after having operated continuously is driven in a continuing manner during stopping of the vehicle, another problem exists in that a larger size is required in order to get a sufficient designing capacity for dealing with heat from the motor generator 3.
In a still further attempt, measures of driving a compressor for vehicles only by means of an electric motor without the compressor for vehicles being connected to an engine, is proposed. In this prior art, however, an inverter unit is required additionally in order to control the air-conditioning compressor for vehicles.
As described above, according to prior arts, any appropriate measure for operating an air conditioner for use in vehicles reasonably during stopping of the engine with a simple arrangement has not been proposed.